In computer-based techniques involving user-machine interaction, the graphical user interface often plays an important role as regards the efficiency of the technique. Many computer systems in general, and CAD, CAE, CAM and/or PLM systems in particular, provide task management and tools in order to help users perform their work in a more efficient way. Task management is also essential to collaborative work.
Methods for tasks scheduling have been described in the literature and there are many commercial and free schedulers available. These include milestone charts, Gantt charts (described in Wilson, James M. (1 Sep. 2003). “Gantt charts: A centenary appreciation”. European Journal of Operational Research 149 (2)), networks, line of balance, and combinations thereof. All have advantages and disadvantages depending on the type of project activity involved. Networking is often preferred for large, one-of-a-kind type projects, but it is not suited to repetitive manufacturing processes. Rather, line of balance or manufacturing flow schedules would be more appropriate. The simplicity and ease of use of milestone and Gantt charts makes them appealing to many managers, but these techniques do not easily accommodate the complexities associated with interdependencies among tasks. All these techniques differ by the nature of considered data, how such data are shown to users, and how the user can interact with the system. Data can be specified by exact values or by approximately known values. The scheduling techniques can differ also by what tasks data are taken into consideration. Some techniques establish a timetable of start and finish times, or a timetable of start times and of tasks durations.
For example, In the Time-Ex (registered trademark) solver described in Kandrashina E. Yu., Markin V. S., Telerman V. V. “Subdefinite models in an intelligent time scheduling environment”, Theory and application of Artificial Intelligence, The II International Conference, Vol. 1, Sozopol, 1989, P. 181-186., tasks are represented by blocks, such as the ones shown in FIG. 1 which represents faithfully a typical screenshot using Time-Ex. Each is appropriately positioned on the time line and stacked vertically. The length of the block corresponds to the maximal possible duration of the event. The left side corresponds to the earliest possible start time, while the right side corresponds to the latest possible finish time. The interval of uncertainty for the start time is represented by a red band in the top left corner. Similarly, a blue band in the bottom right corner indicates the interval of potential finish times. In “Tachyon” (registered trademark), described in Arthur, R., Deitsch, A., and Stillman, J. “Tachyon: A constraint-based temporal reasoning model and its implementation”, SIGART Bulletin, July, 1993, Volume 4, #3, tasks (events) are represented as in Time-Ex, as shown on FIG. 2 which represents faithfully a typical screenshot using Tachyon. The only difference is that Tachyon clearly shows tasks durations. Indeed, the length of the two (black) bands across the center of the block shows the minimum and maximum durations for the event. A recent project management tool named LiquidPlanner (registered trademark) from LiquidPlanner Inc. also uses ranges for task's duration estimation, as shown on FIG. 3 which represents faithfully a typical screenshot using LiquidPlanner. Ranged estimates capture the amount of uncertainty associated with each task. If the range is quite large, the amount of uncertainty is high. If the range is small, the task duration is relatively certain. LiquidPlanner sees each range as a bell curve and uses it to calculate an expected completion date (statistics based).
However, within this context, there is still a need for an improved solution to manage a task.